Variable delivery pump or motor



July 22, 1941- E. K. BENEDEK 2,250,147

VARIABLE DELIVERY PUMP 0R MOTOR Filed June 15., 1938 5 She ets-Sheet 1 1 &-2 3 am ELEKKEJENEUEK u 5,3,4; x0 35 W8 July 22, 1941; a K. BENEDEK VARIABLE DELIVERY PUMP OR MOTOR Filed June 1s, 1938 5 Sheets-Sheet? EL EKKBENEDEK M v fi' July 22, 1941. Q K BENEDEK v 2,250,147

VARIABLE DELIVERY PUMP 0R MOTOR.

Filed June 13, 1938 5 Sheets-Sheet 3 3.? a7 '7 as ix 33a v 36 7 6 as L 6 336 Q 335 mm IL EK K 33 a5 4 :EENEQEK fie 4 MM M July 1941- E. K. BENEDEK 2,250,147

- VARIABLE DELIYERY PUMP OR .MOTOR Filed June 13, 1938 5 Sheets-Sheet 4 531a is J; gala,

Grim/Win 8 E. K. BENEDEK VAR IABLE DELIVERY PUMP CR MOTOR July 22, 1941.

5 Shets-Sheet 5 Filed June 13 1938 s ILEKKBENEDEK Patented July 22, 1941 UNITED STATES: PATENT OFFICE 2,250,147 VARIABLE DELIVERY PIMP R MOTOR 'Elek K. Benedek, Bucyrus qhio Application June 13, 1938, Serial No. 213,325 3 Claims. 01. 103-161) This invention relates to variable delivery pumps or motors ofthe reciprocating radial .piston type, such as disclosed in my .Patent No. 2,166,717.

The primary object of the present invention is to provide synchronized driving connection between the primary and the secondary rotors in a pump or motor of the type herein above referred to.

.A further object is to eliminate driving'forces between the pistons and theirassociated cylinders, in the barrel,incident to the'torque transmission and mechanical driving connections thru the piston and cylinder assemblies themselves between the rotors or from one rotor to the other.

Afurther'object'is to eliminate the mechanical sliding-slip-between .the reactance rotor and the coacting thrust elements carried by the pistons in the other rotor, to thereby provide a more efiicient synchronous drive between therotors.

A further object is to reduce wear and noise andextend the useful life of the bearing constructions, which carry the thrust elements in the heads of the pistons, and thereby. eliminate the possible sliding and subsequent we'ar'of the thrust elements with respect tothe coacting reactance rotor.

A further object is to reduce hydraulic"backlash in pumps and -motors of this type,due to the floating connection between the 'primary and the-secondaryrotor.

In the above said copending application, the guided heads of the radial 'pistons'are equipped with antifrictionally rolling thrust transmitting elements or crosspins. The crosspins are. mounted on anti-friction rolling devices "in the crosshe'ad bores with less frictional resistance, than the frictional resistance between the ends ofthe pins and the associated reactance rotor. The reactance rotor, thru hardened and ground race grooves, engages the-ends of the thrustcross-pin elements for rolling frictional rotation. Only thru hardened and ground racesand cross-pin rollers, and'in case of ,greatenfrictionalengagement at the pin -ends'than-inthe crosshead'pin bearing, is it possible, that the pins will have anti-frictional rolling motion with respeot'to the hardened and groundraces of .therea'ctancerotor and under such conditions, when the radial hydrostatic piston load, which is the thrust load on the cross-pins, is great enough to squeeze out the oil film between pin ends and track races to to metal rolling contact betweenpins and track create rolling friction, can be expected a metal races and consequent rolling motion. At lower operating pressures, when such metal to metal rolling contact is not brought about by the hydrostatic thrust load, the pin ends may slide on an oilfilm or even on the semi-lubricated track races without rolling.

To avoid such sliding motion between the thrust elements or crosspins and the rolling race tracks, I provided in one instance in the above .named application, limited groove means in the reactance so that the pin ends will be limited in their sliding motion by the ends of the limited grooves, at each end of the piston stroke.

In the present application, the grooves which constitute the race rolling tracks arecontinuous. Machining and grinding is thereby simplified and made possible. The limited grooves in the copending application'may cause impact noise at the starting or stopping of themachine by oreating and allowing sharp impact between the ends of the pins and the ends of the grooves respectively. Since such limited grooves permit limited floating movement between the primary andsecondary rotors, it will be'seen that under certain conditions one rotor may be turned with respect to theother, without the rotation of the latter,-to'the extent of the p'lus'margin over the necessary length circumferentially of the grooves, i. 'e. the length of the limited grooves is greater than the relative travel of the pin-ends in said grooves at'the maximum piston stroke.

The said copending application also deals with chordal grooves andsynchroniz'ed piston means. In this application, however, only the circular groove-arrangement is concerned.

The bumping of the pin-ends to the ends of the circular limited grooves has certain undesired effects on the roller bearing equipment of the piston heads'and cross-pins, and its elimination therefore is of the utmost importance for the operation of the pump or motor as a whole,-next to the operation of the bearing equipments.

The construction shown in my Patent No. 2,138,018, utilizes only one single coupling elementat each end of the rotors-and at each side of the piston and cylinder assemblies. Each coupling element engages axially coextensive portions of the primary andsecondary 'rotor'and planetates' about the axis of one of the rotors. Broadly speaking, this construction will permit a floating T-head piston construction, -by alleviating the driving forces from the T-head and associated .reaetance. In the present application, however, the coupling elements are disposed at considerable distance from the axis of rotation of either 10f the relatively adjustable rotors and there is rangement, to thereby change the floating drive to a synchronous drive and to eliminate and change the sliding crosshead shoes of the conventional drive of the prior art into my novel anti-frictionally rolling thrust means, and yet providing simultaneously a synchronized driving connection in the pump or motor. The introduc tion of a plurality of coupling means, other than the thrust means, as hereinafter will be seen, introduces fundamental changes in the construction and operation of the pump or motor. First thefloating drive between primary and secondary rotors will become a synchronized drive, while the tangential driving function of the pistons will be relieved entirely, and confined to radial pumping functions only. Thus the piston relieved from its driving force confines its function to a more radial floating pumping action.

It will be seen that due to the angle between the axis of the piston and the tangent of the reactance groove at its point of intersection with the axis of the piston, there is always a tangential component of the radial piston load acting on the head of the piston, in transverse direction to its axis against the cylinder wall. However, it will be seen that this tangential load component is inherent and its cyclic change is fully determined by the relative position of piston and cooperating reactance, and it cannot be removed by the coupling means. But its harmful effect will be much less in case of a synchronized driving connection by means other than the pistons, than it is in caseof a floating drive, namely, the bearing drag and unbalanced rotary mass forces between the rotors will be unloaded from the pistons and will be taken up by said positive coupling means. The unbalanced mass forces created by the centrically rotating pistons may represent large forces'between the rotors as it may be seen, that the portions of the pistons in the barrel or primary rotor is greatly different from the portions which are out of the barrel and act in the secondary or reactance rotor. All these differences in mass distribution or unbalanced forces will be efliciently taken up by the novel coupling means and evenly distributed there between as hereinafter will be more fully described.

In the drawings:

Fig. 1 isa horizontal main section. taken thru line ll in Fig. 2, showing a pump or motor constructed in accordance with the ideas of this invention.

Fig. 2 is' a transverse sectional view, taken on line 2-2 in Fig. 1. Some of the pistons are shown in section, some of them in elevation.

Fig.3 is a transverse sectional view, taken on line 3-3 in Fig. l, with part of the reactance rotor removed about the piston and cylinder assemblies for the sake of clearance in illustration.

Fig. 4 to Fig. 6 show fragmentary sectional views and elevations respectively of my novel planetating coupling means engaging the rotors for primary and secondary rotors for synchronous rotation.

Fig. 7 corresponds to Fig. 1 and shows another form of the invention.

Fig. 8 is a transverse sectional view, taken thru line 88 of Fig. 7.

In the first embodiment of this invention, as shown in Fig. 1 to Fig. 6 inclusive, the solution is such, that the cylinder barrel I8 is formed with a portion 35 in such a manner that portion 35 contains the cylinders and has a width axially greater than the diameter of the cylinders and terminates radially in a continuous surface at the outer radial limits of the cylinder. This portion is formed with parallel radial walls in a disc-like manner and surrounds, and is carried by the barrel portion l8 which is again rotatably carried on the fixed pintle l2. The barrel I8 is mounted for rotation about a stationary pintle l2 by means of ball bearings 43 supported in the casing. One end of the casing is provided with an axial closure 4 provided with a shaft opening receiving a packing 5 through which a drive shaft 6 extends. The shaft is threaded at 1 to receive a nut 8 which, when drawn up against the adjacent face of the barrel, cooperates with a flange! l on the extreme inner end of the shaft, to secure the shaft to the barrel. A portion H) of the shaft is keyed at 9 to the barrel.

Axially separable and removable reactance halves 26a21a form the reactance rotor, when they abut each other, and are clamped together in a rigid assembly by a plurality of coupling bolts 2828. The reactance rotor is mounted on bearings 2929 in such a manner, that its axis remains parallel with the axis of the pintle and cylinder barrel assembly, in any adjusted position of the reactance. For this purpose, the axial end flanges 26a and 21a of each half are finally supported, in transversely adjustable shifter rings as at 30-38. The shifter rings are shiftably mounted between parallel slide-ways formed with the end covers 2 and 3 of the main housing I.

It will be seen that the reactance halves 26 and 21 are so formed that some of their radially extending portions define closely contiguous radial walls axially'spaced, and permit the intervention of the disc-like portion 35 of the barrel I8. The radially adjoining and additional portions of the halves 28 and 21, define also axially spaced, radially extending and parallel wall portions in such a manner that they permit the intervention of a radial wall 34 of the disc-portion 35 of the barrel. The inner-walls of these portions of the halves as at 25a--2la, and the radial walls of the outside radial flange 35 of the barrel, form radial guide-ways, and guide means respectively for the reactance assembly, during the stroke adjustment of the pump. It is due to this guiding cooperation of the barrel I8 with the reactance, that during every adjusted position of the barrel relative to the reactance, or viceversa, the axis of the barrel and reactance remain parallel with respect to each other.

It will also be seen that when the reactance structure 26-21 is set in eccentric position relative to the barrel l8, and under normal pressure load cycles of the pump or motor, the radial piston load will be transmitted by means of the cross rolling pins 24 to the circular race tracks 26b2lb in Fig. 1, and 2Tb in Fig. 8 respectively. Due to the eccentricity of the race tracks with respect to the axis of rotation of the barrel and the hydraulic piston load, during normal pressure cycles the barrel 18 will drive the reactance 26-21 in case of a pump,:andvice lversa,the re actance 26-21 will drive-the barrel 18 in case .of a hydraulic motor, by the medium of the pistons and their associated piston cross rolling pins"2'4, in synchronisin. But duringlow pressure cycles, outside of the centrifugal forces acting on the pistons 2| and their associated thrust assemblies, such as '23, 2'4 and 25, 'ther'e'is no other force, which would synchronize the barrel with itsreactance or vice versa. It is therefore for such low pressure and other abnormal cycles that the universal coupling means such as 33-33 are provided'betWeen-the'two rotors to effect a synchronous driving and driven relation respec tively, and thereby eliminate the grinding-off of the pin ends of thrust pins on their hardcried and ground race tracks 26b-2'Ib respectively, and assure pure rolling cooperation between the pin ends and their race tracks 2611-2111. 7'

Inthe first case, during'normal pressure cycles, thus synchronism will be provided between the two rotors by eccentricity and rolling frictional depression between thrust'pins and tracks respectively, while in the second' case, namely during low and abnormal pressure cycles, the universal coupling means 33-33 will assume the duty to synchronize the rotors, and thereby to eliminate the slipping and consequent flattening wear of the pin ends of cross rolling pins 24. It will be seen, also, that in order to assure anti-friction rolling motion between pin ends and their respective race tracks 26b-2-l'b during the low and abnormal pressure cycles as in case second, and within the limitsof free tangential reciprocation of the cross pins 24 in their race grooves formed by the inner and outer reactance means 32-32 and 2612-2117 respectively, within themaximum stroke of the pistons and the maximum relative amplitude of planetation of the coupling elements 33-33, thethrust pins 24 are mounted with less frictional engagement in the cross heads 22 on bearings 23, than the rolling frictional resistance ofthe pin ends 24 in their respective race tracks 26b-2'lb respectively. i

The rings 30-30 each is formed with parallel complementary sliding plain faced bearing surfaces, closely fitted, and slidably supported in slide ways, not shown, formed on the inner faces of the end covers 2 and 3 respectively. Shifter rods 3l-3I are provided to shift "the reactance assembly into different adjusted positions, to vary the stroke of the pistons, and the delivery of the pump. The shifter-rods may be fastened to the shifter rings as at 3lb-3lb, while they are further provided with threaded portions as at 3la-3la, to be connected to some suitable external shifting means.

Reactance halves 26 and 21 are provided-with radially extending wall portions which do closely approach the adjacent radial walls of the disc portion 35 of barrel I 8. Between the closely contiguous and radially extending parallel walls of the reactance halves Z6 and '21 and the adjacent parallel walls of disc portion 35 are 'interposed a radial series of planetating coupling element, or universal coupling means such as 33-33, one radial set being disposedat each side of the piston and cylinder assemblies, and between each projecting radial faces of the disc portion 35 and reactance halves 26 and 2'! respectively. The I coupling elements 733 are spaced circumferentially sothat each is disposed mid-'- Way between two ladjacentlcylinders and lies: in a plane containing the" axis of rotation ofwthe cylinderbarreland'the radialaxis of a diamet= ricallyoppositecylinder. 2 Each coupling :element structurally presents a double key, wherein the two keys form. a' rigid cross-like'unit and fastened together "in'suchia manner that their .axes are offset "and disposed exactly at right angles to .each other in their offset planes. Consequently one leg orkeyi'i33a ofthe oross'33 may bevguidedzinbne guider way of one :reactance half'26, while the other'legz33b or key of the cross maybe .guided in a corresponding radial guide-way *36 of the barrel Idisc 35, as shown in Fig. 4 and 'Fig. 6; Thus aicire cumferentially disposed tangential series Jfof grooves '31, in each of the reactance halves 26 and 2l may engage one .leg 33a of each crosslike coupling element .33, a corresponding but radial guide-way as at :36' may engage theradial leg of the same coupling element or unit-.33 in such a manner, that in concentric position with both;rotors, 'i. el-cylinder'barrel 'IB and reac'tance rotor assembly 26-21, each coupling pair 33-33 asshown in Fig. 1 will occupyits center or midposition. The radial guide-ways 36 and the conjugated tangential guide-ways '31, see Fig; '5, are made long enough to allow the necessary movement of the coupling elements 33' and :per mit the free transverse adjustment of the 'two r0tors aboutparal1e1 axis freely and to "the extent of maximum excentricity, relative to each other "corresponding to the maximum stroke 'of the pistons. During relative rotation or adjust ment of the rotors, each coupling pair 33-33 will describe pure harmonic oscillation in their grooves relative to their carrier members, :i. i the disc' 35 and the reactance halves :26 "and .121, and they will planetate about the axis of rotation; which =isthe stationary .axis of thebarrel I8 and pintle 12 respectively. 7

One of the outstanding features :of this structural arrangement lies in the compactness and effectiveness of the coacting coupling means. First the coupling'units-33are evenly distributed around the axis ofrotation, and at a substantial radial distance therefrom. Secondly, the" radial walls of disc 35 and halves .25 and 121 are 'so'. closely disposed that the elements 33 are sub ject only to shearing stresses, and they work'ex= actly as a key member or machine element in their respective Ways, to transmit large torque or force with a relatively small'key-bo'dy-l This means that the addition of the masses of the keys33 to the masses of rotation'are "negligible and do -not*affect.niaterially the dynamic balance of the pumpor motor. 'Becauseone of the main difliculties inhigh speed machines is, to main tain in proper balance the rotating assembly, irrespective of whatever means are used for coupling purposes, it will be seen that the coupling elements=are so small and evenly distributed circumferentially, that even in their off center positions their resultant center of gravities lies substantially in the axis of rotation of the barrel. H I Aradial series of piston and cylinder assembly is disposedabout the pintle 12, which is provided with the conventional external and 'internal main ports as at I l-I5 and IE-Hire spectively. The corresponding ports are ag'ain in communication bymeans of appropriate ducts 14-44 and 45-45 as shown in Fig. 3.

Each cylinder l-Eis alternately in co'mmunic'a tion with one-of the individual pintle ports '13 or H thru its port 20. Each cylinder're'ceives verse crosspin 24.

airadial piston as at 2|, which piston'is sus-' pended in the reactance by means of a trans- Each crosspin, after being finished and polished to precision size is mounted in a piston cross head vhole and on appropriate: elongated anti-friction roller; bearings such as 23. -Means inserted at the endsof the roller-bearing elements in the crosshead bores such as' 25-25 are provided to retain the roller bearing elements in their operating. relation, between piston bore and crosspin. The members 25 may be simply. pressfitted' intothe ground and polished piston-head bore or they may be made integral with the heads," as a matter of choice of thedesign.

The reactance halves 26 and 21' are formed with circumferential and normally aligned shoulders 26b21b respectively, as race tracks on which race-track ways the pin-ends of pins 24 bear with rolling frictional engagement-and in such a manner, that the axis ofthe pin 24 will remainparallel to the axis of the rotation of the machine, and with greater frictional resistance at the pin ends than at the rollers'23 and the pins 24 in the crosshead-bores. Under such conditions the pins will roll on the respective tracks 26b and 21b, substantially under allnonnal load operating conditions. Track-ways 26b "and 21b are hardened, ground and polished, in order to promote efi'icient and pure rollingcooperation at these points by metal tometal rolling contact and thus to eliminate possible mechanical slip and hydraulic back-lash between" the track-ways 26b2'lb on the one side, and 24 on the other side, and thereby between the two rotor assemblies. The sliding motion of the pin-ends is furthermore eliminated or limited by the positive coupling means 3333 between the rotors as hereinabove was more fully described. It will be noted that the nature of the contact and coaction between the pin ends 24 and the race-tracks 26b and 21b is a very delicate one. 7 It is obvious that at the rolling contact points of pin ends and hardened tracks, the wear and continuous abrasion of the parts will be'elimihated only if during the rolling motion of the pins, there will be an efiective oil film and good lubrication around the pins. This lubrication and oil film will preserve the pins as rollers-by cooling them thru heat conduction, in spite of the fact that at the instantaneous line contact between pin ends and tracks, the oil film is destroyed by the pressure, and a momentary metal to metal contact is created. The capillary drawing of oil film into the wedge-shaped space in front and rear of the rolling pins between the pins andtracks, issufficient to coolthe elastic depression created by the instantaneous metallic contacts. This metallic contact is obtainable by the use of my coupling elements which relieve the pins of torque transmission and assure rolling contact only of the pins and .tracks25b and Anydamage at this point eitherto the pins or to the tracks would result in complete failure'of operation. Sliding would cause eventual galling welding or flattening of the pin ends. Galling would prevent rotation of the rotors and reciprocation of the pistons. Second, when'the device is utilized as a motor, the power is derivedpright from this point of the motor. The torque efficiency of a hydraulic motor thus hinges entire- 1y on the efiicient way, at which the thrust means and reactance cooperate. Hence, the sige nificance of assured anti-friction rolling coaction in this device, since it is more efficient than sliding frictional coaotion with large sliding shoes and plain bearing surfaces.

Furthermore, the rolling pins 24 are naturally disposed with respect to the reactance race tracks 26a. and 21a with a certain-unstable rolling relation, ready to start rolling and exert starting torque to the motor, under the slightest working pressure of the motor, while large sliding load transmitting shoes at this point act like braking shoes of a hydraulic'brake. The more pressure is applied radially to the brake the harder it will be to move the shoes. This will lock the rotation like brakes, instead of imparting movement. Thus the assurance of anti-frictional rolling engagement between cross-pins 24 and reactance tracks 26a and 21a is not only equivalent with the maintenance of commercial efficiency, but the utility of a hydraulic motor and its-starting torque quality is entirely dependent on this distinct feature. This quality is so essential fora useful motor, now lacking in many commercial pumps, that not all hydraulic pumps are usable as motors. Briefly, pumps are not ordinarily reversible as motors. Thus reversibility of a hydraulic pump is the real criterion of double utility as a pump and a motor.

In order that not only the shoulders 26b and 21b may be finish ground, but their radial end walls also, the inner race tracks 32-32 are formed of independent rings. This makes a highly practical and precision track arrangement possible for thecross-pins, as being commensurable with the importance of this type of mechanisms.

The modification of Figs. '7 and 8 shows similar coupling elements as at 3838, with the difi'erence in their location only in the connected assemblies.

Instead of the disc portion 35 of the barrel I8, the flange portion 34 is utilized for the location of radial guideways 4|4l of the coupling elements 3838 in the barrel. The circumferential track ways in the reactance halves, formed by shoulders 26'b and 2Tb and the associated floating rings 3232 respectively are utilized-for locating the corresponding tangential groove-ways for the coupling elements 3838 in appropriate circular segment-blocks 39-49. Each block element 39 is fastened to its reactance half 26 or 21' risialbctively, by appropriate means such as shown a In this modification the working torque arm of the elements 38-38 is greater, consequently their size can be smaller for the same amount of torque.

Thus the plan view of the arrangement of the coupling elements '38, in their respective blocks 39, with the tangential ways 42 is well illustrated in Fig. 8. It will be seen that in this second modification, full advantage is taken of-the reactance grooves between each pair of consecutive pistons to receive the block elements 39 for receiving portions of the coupling elements 38, with the advantage that the block elements 39 are now adjustable circumferentially to'match the radial grooves 4| before pullin the screws 40 tight or fastening them to the reactance halves 26' and 21' respectively to secure the blocks 39. The adjustability of the guide block elements 39 is very slight, being provided by the clearance that exists between the sides ofthe fastening elements 49 and the sides of the holes in the reactance-halves 26' and 21' through which they extend. However, this slight adjustability is all that is needed to compensate for the inaccuracies of alignment of the guideways 4| and 42 that may arise in manufacture.

Various changes may be made in the embodiment of the invention, without departing from or sacrificing the advantages as defined in the appended claims.

I claim:

1. In a pump or motor, a pair of rotors in eccentric relation to each other, radial piston and cylinder assemblies carried by one of the rotors and operated by the other consequent upon concurrent rotation of the rotors, valve means for the assemblies, one of said rotors being in surrounding relation to the other rotor, an adjustable guide means carried by one rotor and spaced radially from the axis of rotation thereof, a radial guide-way carried by the other of said rotors and in fixed position relative thereto and extending radially inwardly and outwardly beyond both radial limits of said adjustable guide means, and a coupling element having portions engaged with and slidable along said guides respectively concurrently, and being operative independently of and disassociated from the piston and cylinder assemblies, said adjustable guide means, including an adjustable block element, havin a chordal guide-way therein, and means to secure said block element rigidly in its respective rotor,

after the coupling element has been assembled in its respective guide-ways, to thereby provide self alignment between the guide-ways and the coupling element.

2. In a radial piston pump or motor, a rotatable barrel having radial cylinders, a portion of the .1

barrel in which the cylinders are located being of greater Width axially 0f the barrel than the diameter of the cylinders and terminating outwardly in a circumferentially continuous surface, and said cylinders terminating outwardly in said surface, valve means for the cylinders, pistons reciprocable in the cylinders respectively, an adjustable reactance rotor eccentric to the barrel and having spaced walls at opposite sides of the rotational path of the pistons, said walls having parallel slideways, a pair of coupling members connected to the reactance rotor, .each of said members comprising universal cross-like coupling elements having offset keys disposed at right angle with respect to each other, one pair of said crosslike coupling members being received in one pair of said slide-ways for oscillation there-along, a

flange on the barrel extending radially outwardly beyond the circumferentially continuous surface of the said barrel portion, pairs of parallel Ways in the flange respectively circumferentially midway between each two adjacent pistons and each pair of ways being in a plane containing the axis of the cylinder barrel and the radial axis of a diametrally opposite piston, said flange ways receiving respectively the other elements of said cross-like coupling members, for reciprocation therein, said slideways being aligned axially of the rotors to form a conjugated pair of guide Ways and to receive the crosslike coupling members for planetating movement with respect to the combined rotors, and thereby connecting the barrel and reactance rotor for synchronous rotation.

3. In a radial piston pump or motor, a rotatable barrel having a cylindrical body, radial cylinders in said body terminating at their outer ends at the outer radial limit of said body, valve means for the cylinders, pistons reciprocable in the cylinders, said barrel having a radial flange rigid therewith and extending outwardly from the outer radial limit of said cylindrical body, radial guideways in said flange extending parallel to the axes of said cylinder, heads on the pistons guided for radial reciprocation in the guideways, a reactance rotor eccentric to the barrel, said reactance rotor including spaced walls disposed at opposite sides of said flange and having coupling guideways and thrust element guideways in said walls, coupling elements having portions slidably received in said coupling guideways for oscillation there along, coupling guideways in the flange of the barrel and perpendicular to the coupling guideways in said reactance walls and receiving other portions of said coupling elements, rolling thrust elements received in said thrust element guideways for oscillation there along and connected to the pistons for actuating the pistons, said coupling guideways in said barrel flange extending parallel to the axis of the diametrally opposite piston and lying in the plane defined by the axis of the barrel and the axis of the diametrally opposite piston, said coupling elements being disassociated from the pistons and thrust elements and being the principal means for effecting synchronized rotation of the barrel and reactance rotor.

ELEK K. BENEDEK. 

